The goal of these experiments is a better understandng of pulsatile blood flow in the mammalian circulation. Specifically, we seek to identify and describe systematically: (1) the factors that determine the pulsatile characteristics of the pressure and flow waves generated by the heart; (2) the transmission and transformation of these waves as they travel through regional vascular beds; (3) the mechanisms by which these phenomena are controlled and modified to meet the changing needs of the organism. Input impedance and net transmission through certain major regional beds (renal, splanchnic, cerebral, muscular, et. al.), the changes that accompany normal activity, and the influence of the autonomic nervous system will be investigated through experiments on intact dogs, perfused organs, and isolated vessel segments. The viscoelastic properties and anatomic features that are hemodynamically relevant in these vascular beds will also be measured. The physiologic and clinical significance of the information sought in this work lies in the fact that the elasticity of blood vessels determines in part the work demanded of the heart, and the observation that the function of some systems is influenced by the amount of pulsation reaching the capillaries.